Digital lighting technologies, i.e. illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626, incorporated herein by reference.
In certain lighting fixtures implementing LEDs there is motivation to limit or eliminate the amount of light from the LEDs that is directed from the lighting fixture to areas that are not intended to be illuminated. Motivations to limit such stray light from LEDs may include the desire to achieve compliance with one or more standards. For example, obtaining credit for Leadership in Energy and Environmental Design (LEED) certifications requires conforming to specified spill light levels in lighting layouts. Current designs directed at limiting the amount of stray light from LEDs may significantly reduce the efficiency of light directed at the intended illumination area. Current designs may additionally or alternatively fail to limit stray light to the degree necessary to achieve compliance with one or more standards such as compliance with requirements specified by LEED.
Thus, there is a need in the art to provide an optical system for LEDs for control of light output from the LEDs that optionally overcomes one or more drawbacks of some current designs.